It is known to generate an index entry in conventional recording of image/sound of a state in which a person who writes a description is explaining while writing a description in a description portion. For example, in Patent Document 1, a method of generating an index entry is proposed, in which the index entry is generated when the writing of the person who writes a description is interrupted for a predetermined time. However, the index entry is not generated on the basis of the content of the writing by this method, and the index entry is not generated unless the writing is interrupted. Therefore, in reproduction, it is difficult for a viewer to reach a desired reproduction start position referring to the index entry.